The present disclosure generally relates to depth sensing, and specifically relates to ultra-wide field-of-view scanning devices for three-dimensional (3D) depth sensing.
To achieve a compelling user experience for depth sensing when using head-mounted displays (HMDs) and near-eye displays (NEDs), it is important to create a dynamic and all solid-state light scanning device with both ultrafast scanning speed (e.g., MHz) and large field-of-view. Usually, there are tradeoffs between speed, field-of-view and real-time reconfigurable illumination characteristics. Typically, a microelectromechanical system (MEM) having a mechanical-based mirror device can be used for scanning. However, the mechanical-based mirror device has stability issues and has a limited scanning speed. In addition, the mechanical-based mirror device is not reconfigurable in real time applications.
Most depth sensing methods rely on active illumination and detection. The conventional methods for depth sensing involve mechanical scanning or fixed diffractive-optics pattern projection, using structured light or time-of-flight techniques. Depth sensing based on time-of-flight uses a MEM with a mechanical-based mirror device (scanner) to send short pulses into an object space. The depth sensing based on time-of-flight further uses a high speed detector to time-gate back scattered light from the object to create high resolution depth maps. However, the mechanical-based scanner performs inadequately in relation to scanning speed, real-time reconfiguration and mechanical stability. The scanning speed is often limited to a few kHz along a fast axis and a few hundred Hertz along a slow axis. In addition, the mechanical-based scanner has stability and reliability issues. Depth sensing based on a fixed structured light pattern uses a diffractive optical element to generate a fixed structured light pattern projected into an object space. The depth sensing based on the fixed structured light pattern further uses a pre-stored look-up table to compute and extract depth maps. However, the depth sensing based on the fixed structured light pattern and the diffractive optical element is not robust enough for dynamic depth sensing.